Telephone system



F. LUBBERGER ET AL Sept. 14, 1937.

TELEPHONE SYSTEM Filed June 19, 1935 4 Sheets-Sheet l INVENTORS FRITZ LUBBERGER BENNO JOHANNESSON Zfl ATTORNEY.

F. LUBBERGER ET AL 2,093,246

Sept. 14, 1937.

TELEPHONE SYSTEM Filed June 19, 1955 4 Sheets-Sheet 2 Em NNzm 3m INVENTORS FRITZ LUBBERGER .BENNO JOHANNESSON ATTORNEY.

Sept. 14, 1937. F. LUBBERGER ET AL 2,093,246

TELEPHONE SYSTEM 3min) REGISTER INVENTORS FRITZ LUBFERGER BENNO JOHANNESSON' ATTORNEY.

F. LUBBERGER ET AL TELEPHONE SYS TEM Filed June 19 1935 4 Sheets-Sheet 4 136 a FIG 9 13568 LW7 a 7 s4 s1 0 $1 7 r1 o 1 u g I 1195s 1 12058 4% H B'b'sY SJ T NE ' ATTORNEY.

Patented Sept. 14, 1937 UNITED sr assign;

TELEPHONE SYSTEM Fritz Lubberger and Benno J ohannesson, Berlin, Germany, assignors to Siemens & Halske Aktiengesellschaft, Wernerwerk,

near Berlin, Germany Siemensstadt,

Application June 19, 1935, Serial No. 27,459 In Germany June 20, 1934 13 Claims. (01. 179-9) This invention relates generally to a circuit arrangement for telephone systems in which call registering and automatic ring back on the release of the called line are provided. According to the arrangement, switching means are provided which upon the initiation of a waiting period, maintain the call route set up to a subscribers station, independent of the station which has produced the called condition.

The present invention is directed to further improvements in such circuit arrangements and comprises means whereby upon the replacement of the receiver by the calling station subsequent to dialing, the call is automatically registered by switching means and the ring back is transmitted depending upon a switching condition of the desired subscribers station. The calling station thus need not operate special switching means for the initiation of the waiting condition, which, in the case of systems which possess such switching means, can easily be forgotten. Moreover, according to the present invention this. waiting condition takes place automatically. The method of using the system is thus simplified.

The further characteristics of the invention are disclosed in the three embodiments comprising Figs, 1, 2, 3, and 4, described below.

The embodiment illustrated in Fig. 1 shows a system in which the waiting station sets up a call to the desired station and afterwards replaces the receiver. On the replacement the reg istering takes place automatically. The ring back then takes place according to the invention upon the desired called station replying so 'that the waiting station is immediately connected with the desired station on removing the receiver when the ring back is obtained-an arrangement which is included with advantage in systems in which the registering does not occur automatically. The arrangement facilitates for the privileged subscriber not only waiting for the desired called station to be released but also the waiting for the reply from the free called station. If the waiting subscriber wishes to effect another and important call he need only remove his receiver to receive a free call route.

The ring back in Fig. 1 is made to operate through the receiver of the waiting subscriber so that without providing a separate receiving device he receives the ring back in a different way from the usual ringing.

The ring back is initiated by the means which in the usual system serves for preparing the metering; namely by the connection of earth to the a-lead on the reply of the desired subscriber.

In the embodiment according to Fig. 2 a further known means, namely, the so called seizing means which consists in earth to the b-line is used, for giving the busy signal when the desired subscriber is engaged. In the second embodiment call registering is only possible in thiscase. If the subscriber who is entitled to wait replaces the receiver call registering is effected. On the desired called station whose testingis repeated at definite intervals, replying, the ring back is initiated by the metering means as in the case of the first embodiment. In case the waiting station does not answer again, the call route is set up or released by means of a time'switch.

In the case where the desired calledstation consists of a private branch exchange the final selector switch tests these lines and if all the lines are engaged it remains on the last of these. Then the same switching process comes into play as in the case of the final selector being seti on a single line.

Systems with main stations'and privateb'ranch stations are so constructed that the waiting for the private branch station is made convenient for the calling station. After the calling station has informed the main station of its desire to speak to the private branch station and the main 3o station has extended the call, both the calling station and the main station can replace their receivers. On the private branch station replying ring back is sent to the waiting station.

In both the embodiments mentioned the connecting path set up to the desired station remains seized during. the waiting period. This, particularly when a long waiting period is in question, involves a considerable load on the system. The number of selectors must be made larger than for the usual system without waiting devices. According to the embodimentof the invention shown in Figs. 3 and 4, a call number register is arranged which receives the number of the desired station and repeats the setting up of the call periodically. The connecting path seized meanwhile can thus be again released shortly after its establishment, in the case of unsuccessful calls, so that the selectors may be used for other calls. 50 By the use of this arrangement the waiting period may be prolonged for hours without particularly burdening the system. This is particularly important when a privileged subscriber urgently wishes to reach an absent called subscriber. The absent. subscriber is rung at definite intervals the connection of 5- provided which of course can be attached to several subscribers in common.

In the third embodiment the registering also occurs automatically. Naturally the principle of the invention shown in Figs. 3 and 4 is not limited to this arrangement, but on the contrary this particular call registering can also be initiated by the operation of a switching device on the part of the subscriber privileged to waiting service, for example, by the waiting subscriber depressing a key or dialling a particular number.

'In the last case the common registering device can be reached over selectors, by dialling.

The first embodiment will now be described in the following description with reference to Fig. 1.

The invention is applied to a well known system, which is represented in Lubbergers book Telephone Systems Operated by Selectors, 4th editiompublished in Germany, in Fig. 187 and is described on pages 158 to 161. In order to apply the invention to sucha system, it is merely necessary to connect the final selector LW with the contact of "atesting selector PW and to modify the switching of the pre-selectors and first group selector of the station entitled to call registering by the addition of a relay. For the normal subscriber the setting up of a call is not altered in any way by this. They merely have the opportunity, through the addition of selector PW, of "Waiting with" the receiver to the ear for the release of the dialled connection. The selector PW isattached to several final selectors in common and either rotates continuously or is set in motion on'the seizing of a final selector of the final selector group attached to it.

The switching process for the setting up of an outgoing call by privileged subscriber N I, Fig. 1, is as follows:

On the removal of the receiver the pre-selector VW is set on a free first group selector IGW; The pre-selector is started up by the corresponding calling relay R. In the testing circuit relays 'T and C energize and the testing relay G partially energizes, on reaching a free first group selector over the circuit: negative battery, wiper d of pre-selector VW, contact Ir, relay T, winding I ofrelay G, winding I of relay C, off normal contact is of the first group selector IGW, pole battery. The loop isswitched through at con- I tact 2t and 3t so that relay A in the group selecfinal selector.

tor energizes. The subscriber NI receives the dialling tone transmitted over winding II of relay A: pole, winding II of relay A, contact 4a, rotary ofi normal contact 510 of the group selector, dialling tone transmitter AZ. The privileged subscriber sets the selectors of the connecting path by means of dial impulses in the known way. This is unafiected by the number of group selectors provided. By setting the first group selector IGW the rotary off normal contact 5w isswitched over so that the dialling tone is disconnected. The two last impulse trains are taken up by the final selector LW. They are transmitted in the known way from the group selector over the a-lead to winding I of the relay All of the The seizing of the final selector occurs in the known way by energizing relay CI over the o-lead. The tens impulses of the final selector are taken up by the vertical magnet H, over the circuit: pole, contact Gal, winding II of relay V, contact 45a, rotary off normal contact 8w'l of the final selector, vertical magnet H, pole. In the circuit relay V energizes over its winding II. It holds up during the impulse pauses throughout the impulse train on account of the short circuit of its winding I. After the switching according .to the tens digits relay V releases so that relay U energizes over the circuit: pole, vertical magnet H (at present not yet energized) contact 8wl,, winding of relay U, contacts 9cl,

, I012, off normal contact I lkl, pole. The rotary magnet is operated on the units selection and at the same time relay V is again energized over the circuit: p0le,'contact Gal, winding II of relay V, contacts Tu, lZp, rotary magnet D pole. Relay U remains energized during the impulse train, in the following circuit: pole, winding II of relay U, contacts I312, Mu, l5c pole.

On the termination of the units selection relay V again releases and connects testing potential through contact 4512 but only as long as the slow acting relay U keeps its contact Mu closed.

, If the subscriber is free relay P energizes over: pole, contacts I50, Mu, I312, relay P, c-lead of the final selector LW, subscribers relay not shown, pole. In thisoase the subscriber N2 receives ringing current periodically over contact H50, in the circuit: ringing current source, contacts I60, I'lp, a-lead, subscribers station N2, b -lead contact i817, winding I of relay Y, pole. The periodic energizing of relay V takes place over the 10 second switch: pole,.non-energized rotary magnet D, contacts 46p, l'ly, Winding III of relay V, contacts 2611., 10 second switch, pole. Part of the alternating ringing current is transmitted tothe calling subscriber over condenser C2 as a ringing, signal. On the reply of subscriber N2 relay Y energizes in the ringing circuit. Contact lily produces the metering operatact 242, relay Z, contact 220, pole. Relay Y locksitself up in the following circuit: pole, winding I of relay Y, resistances Wil and Wi2, choke coil Dr, winding III of relay Y or contact 232), contacts I9y, 46p, rotary magnet D, pole. The metering is operated at the end of the call in the case of known systems, in which for example, a potential is applied to the c-lead of the pre-selector which causes the energization of the meter arranged in parallel with the subscribers relay, The meter is notincorporated, however, in the embodiment.

As noted at the beginning the privileged subscriber NI need not, according to the invention, continue listening with the receiver until subscriber N2 replies. He can replace his receiver immediately upon completion of the last impulse train. The release does not set in then, because the short circuit of relay C of the first group selector at contact 259! of the partially energized relay G, which is caused by replacing the receiver in the usual systems, is prevented. When subscriber N I replaces his receiveronly relay A deenergizes. The following circuit for the hot wire relay Th2 is thus completed: pole, hot Wire relay Th2, contacts 44gl, 39a, 30c, resistance Wi4,v

contact Bin, pole. If the desired subscriber does not reply within the energizing period of relay Th2, which may be 30 seconds relay C is short circuited at contact 2915722. At contact 300 the locking circuit for the pro-selector is released; pole, contact 3111., resistance Wi l, contact 30c, windings II and I of relay C, winding I of relay G, c-lead of pre-selector VW, relay T, contact 321., wiper d of the pro-selector, pole. The preselector returns to the rest position. At the same time the other selectors of the connecting path are released. The hot wire relay TH! remains energized over contacts 28th! and 21k until the group selectors are released.

If, however, the subscriber N2 replies before relay TI-IZ energizes, relay Y is energized in the final selector LW as described above and the metering operation is transmitted back to the first group selector IGW over the b-lead, so that relay Z energizes there. At contact 332 the following circuit is completed for Winding II of relay A: pole, winding II of relay- A, contacts 5a, 332, 340, 359 II (completely energized), buzzer. The buzzer signal is transmitted to the winding I and III of relay A attached to the speech leads and is brought to bear on the receiver of the waiting subscriber Ni. In order to make this buzzer circuit possible the receiver of the privileged subscribers station is not disconnected from the line on replacement but remains connected through a condenser. The condenser is con veniently so adjusted that the buzzer circuit mentioned is tuned to the frequency of the buzzer. The signal is chosen to be of such an intensity that the subscriber can hear it from a distance. On hearing the special signal the subscriber N2 knows that the call for which he is waiting is involved and not some other new call. On taking up the receiver the direct current circuit to station N1 is again established. Relay A again enerizes over its windings I and III. The primary buzzer circuit is broken at contacts 5a. The subscriber N! can thus speak to subscriber N2 immediately after lifting his receiver. On subscriber N! replying a circuit is completed for winding II of relay G at contact 4a: pole winding II of relay A, contact 4a, rotary off normal contact 3610. contact 31.2, winding II of relay G, pole. Relay G energizes completely so that the short circuit of relay C is prepared at contact S8gII. When the subscriber replaces the receiver at the end of the conversation the short circuit of relay C is completed at contact 39a.

The release of the connection occurs in the known way. It is initiated on subscriber NI replacing his receiver.

If the desired subscriber N2 is engaged, however, in another connection, relay P cannot energize, after the last impulse train has been transmitted within the time taken by relay U to release. Subscriber Ni accordingly receives the engaged or busy signal through winding II of relay Al z-l-pole, winding II of relay Al, rotary off normal contact 2910!, contacts My, Mp, busy signal. On receiving the busy signal subscriber Ni replaces the receiver and, as described above, effects the registering of the call. The testing circuit for relay P is always prepared over the contact wiper of selector PW at contact I31), when this wiper passes over the contact connected with the final selector LW. If at such a moment the desired subscriber has become free, testing relay P energizes. The further switching process takes place as in the case or" subscriber N2 being free, as described above. When subscriber N2 replies the metering operation is again brought about, and the ring back thus initiated.

Let us assume that subscriber NI wishes to set up another call within the waiting period, and before the hot wire contact ll'il'bl has made contact. After replacing his receiver the circuit for relay THE is completed over contact 5a and off normal contact 21k. This energizes after about one second and locks up over its contact 28th! independently of contact 5a. At contact 42ml a circuit is prepared for relay N. This circuit is completed when the subscriber removes his receiver in order to set up another callz-l-pole winding II of relay A, contact 4a, rotary off normal contact 36w, contacts 432, 4225M, relay N, -po1e. Relay N energizes. It is of such high resistance that it cannot affect relay A. At contact 3111. the locking circuit for relay C is broken, so that this relay releases and the connection maintained during the waiting period is released. The preselector is then further operated and seizes another group selector, which is set by the subscriber in order to bring about a new call.

The embodiment illustrated in Fig. 2 uses the known seizing means for preparing the registering. This consists in that earth is connected to the a-lead in the final selector which is transmitted to the first group selector over the selector wipers and there operates a relay. The ring back can only be transmitted when the seizing opera tion has previously been brought about. As in the first embodiment the ring back is also released in this case by the metering operation (earth in the b-lead).

The registration is prepared by the transmission of the seizing means, I on finding the subscriber engaged, and 2 on Waiting for the reply of a private branch station subscriber. If the desired connection is a private branch exchange, the group is then hunted through. On finding the last line of the several line connections engaged the seizing means is transmitted.

A well known telephone system for example that illustrated in Lubbergers book Telephone Systems Operated by Selectors (4th edition) in Figs. 116/120 is used as a basis. The parts used for registering and ringing back can be incorporated in the known systems without further alteration. The subscribers entitled to registering are provided with a special first group selector. The other group selectors are of the normal type. The final selectors are modified by the addition of a relay RME and a choke coil Drb. The relays otherwise connected to the incoming aand b-leads of the final selector can thus be omitted. Thus the same relay base can be used for the final selector merely with the difference that two original relays are replaced by two new ones.

In Fig. 2 only those switching means necessary for understanding the principle of the invention are illustrated.

It is assumed that a subscriber N5 entitled to call registering sets up a call to a subscriber N6.

On taking up the receiver the pre-selector VW5 is set in the known way on a free first group selector IGW5 which is provided with the necessary switching means for recording the call. Relay Ct energizes over the c-wiper of the preselector VW5. Relays A5 and B5 are energized over the connected speech leads. Through contact 5505 the following circuit is completed: pole resistance Wz'E, contact d905, winding II of relay C5, winding I of relay V5, +pole. In

this circuit relay V5 energizes, whilst relay C5' switch occurs through relay F5.

looks up independent of its winding I. The first group selector IGW israised to the desired level in the known way under the control of relay A5, and there seeks automatically for a free line leading to a final or second group selector. In the first vertical step the off normal contacts marked it are operated. Relays P5 and C5 energize over the .c-lead. 1

The final selector is set in the known manner by two impulse trains. A control switch system forms the basis of the embodiment. The contact paths of the control switch are indicated by roman numerals. The control of the control On the completion of the selection the control switch moves to position l. Over contact 1V6, a testing circuit is prepared for relay P6. If the subscriber is free the test relay P5 energizes. The control switch is thereupon advanced to position 5. It is also advanced from this position by the energizing of relay F5, over the circuit:+pole, contact 53p6, control switch I5, relay F5, pole. Relay RM5 does not energize through its winding II, because it is short circuited through contact 5511-8. In position 5 for example subscriber N5 is rung for the first time. The periodic further ringing takes place in. position '7. When the desired subscriber replies the control switch moves on to position 6, which is the first speaking position. The speech line is switched through at contacts 1115 and IVS. The termination of the call takes place in the known way.

If, however, the subscriber N6 is engaged the following switching processes are effected:

In control switch position 4 relay P6 cannot energize. The control switch thereupon proceeds to position 5 in which it remains since relay F5 does not receive sufiicient current in the circuit: pole, relay F5, control switch I5, multiple contact mk5, winding II of relay RM5, pole. Relay RM, however, energizes and in correspondence with the seizing means connects earth to the a-lead over contacts 55rm5 and 5406. The earth potential is not operative yet because contact 5505 in the first group selector IGW is now open. The calling subscriber receives the busy signal in the known way and replaces his receiver. Accordingly relays A5 and B5 in the first group selector release. Contact 52a5 short circuits the winding 11 of relay C5. The latter deenergizes. Contact 45305 opens the locking circuit for winding I of the slow acting relay V5. Before the release, however, a circuit is closed for its winding II, because in the meantime relay RR5 energizes on account of the earth attached to the a-lead in the final selector: pole, contact 5406, winding I of the choke coil D15, contact 55rm5, a-line, contact 5505, relay RR5, pole. At con.- tact 51??"5 relay RR5 completes the following circuit for itself and the above mentioned winding II of relay V5: pole, relay RR5, contact 51MB, winding II of relay V5, contacts 58b5, 59:05, 60k, pole. Relay V5 remains energized together with relay RR5, although its winding I was disconnected on the subscriber N5 replacing his receiver.

At definite intervals of time the desired subscriber N5 is tested to find whether he has become free.

The selector PR5 is used for this purpose, to the contacts of which the relays P6 of the different final selectors are connected through the contacts iiirm5. In this Way the selector PR5 prevents a double testing from taking place. When the subscriber N6 is free relay P6 energizes over: pole, wiper of selector PR5, contact 6Irm5, test relay P6, c-wiper of the final selector LW5, subscribers relay of subscriber N6, pole. At contact 53116 the winding II of relay RM5 is short circuited, so that the control switch is moved from its position 5 by the energizing of relay F5. As described above the ringing of the desired subscriber N6 takes place in the further positions of the control switch. On the subscriber replying the control switch moves to position 8, and the potential serving to prepare the metering is attached to the b-lead: pole, winding II of the choke coil Dr5, control switch VB, b-lead contacts 6205, 63rr5, relay Z5, contacts 59:05, 66k, pole. Relay Z5 energizes and completes a circuit for winding II of relay A5, buzzer SU, contact 6425, winding II of relay A5, contact 6555, buzzer SU. By transmission from winding II to winding I of relay A5 the subscriber receives a powerful buzzer tone in the receiver, as in the first embodiment. On subscriber N5 replying relays A5 and B5 again energize. Relay C5 is again energized over contact 6655: pole, resistance Wi5, contacts 5lc5, 6125, 66b5, winding II of relay C5, winding I of relay V5, pole. At contact 58b5 the locking circuit for winding II of relay V5, and for relay RR5 is broken. Relay V5, however, holds up over its winding I. At contact 63rr5 the circuit for relay Z5 is broken, so that the buzzer circuit is also broken. 7

In order that the seized connection path should not be withdrawn indefinitely from the service a hot wire relay TH5 is arranged in the first group selector. As described above the call registering is prepared by relay RR5 andis operated on subscriber N5 replacing his receiver. Relay C5 thereupon releases and completes the following circuit at contact 6805; pole, hot wire TH5,

contacts 6805, 59135, ofi normal contact 60k, pole. Relay TH5 energizes after a definite period for example after thirty seconds, if the subscriber N5 has not replied in the meantime. This case can occur if either the ring back is not given, or the subscriber does not reply on receipt of the ring back.

If the line dialled by subscriber N5 is a private branch exchange, then, after the final selector has been set on the first line of the several line connections, the lines of this are then tested. If none of the lines are free the final selector remains on the last line. While the several lines of the group were being tested in position 5 of the control switch, relay RM5 could not energize because the multiple contact mk5 is only closed on the last line of the several line connections. The switching processes taking place on this line are the same as in the case of a single line connection. Thus in the case of the last line being engaged the call registering is first prepared, and on the subscriber becoming free and replying the ring back to subscriber N5 is released.

If the station of the desired subscriber N6 is a main station, the calling station N5 has the possibility of replacing the receiver during the period of waiting for the reply of the private branch station. The switching proceedings are as follows:

The call to the main station takes place over the control switch position 8. If a private branch station is required the main station transmits the call to the private branch station and then replaces the receiver. Thereupon the control switch proceeds'to position 9 in known manner which will not be further described here. In this position relay F5 energizes over pole,

Winding I of relay RM5, control switch I9, relay F5, pole. Relay F5 cannot energize in this circuit on account of the high resistance of winding I of relay RM5. The call registering is prepared over contact 55rm5, as described in the case of the subscriber being engaged. On the replacement of the receiver by subscriber N5 the call registering takes place. When the private branch station replies relay A6 of the final selector energizes and at contact 690.6 short circuits the winding I of relay RlVI5, so that relay F5 energizes and the control switch moves on to the second speaking position 10. pole is connected to the b-line over the control switch contact Vii so that the call back is initiated.

The third embodiment is illustrated in Figs. 3 and 4.

In this case the setting up of the call is repeated periodically, as noted already in the introduction, until the call can take place. Thus the connecting path can be used during the waiting period for other calls. In the embodiment the call is always released after it has been set up again, if the desired subscriber is found to be engaged.

The known Director system forms the basis of the embodiment and is described, for ergample, in Lubbergers book Telephone Systems Operated by Selectors, 4th edition, on pages 263 et seq., and is illustrated in Fig. 130. In order to make the principle of the invention clear only such of the known switching means are shown in the embodiment, as are absolutely necessary for understanding the invention.

The setting up of the call takes place over preselector, group selector and final selector, for example from subscriber N! to subscriber NB. The impulses are taken up or recorded and automatically transmitted to the speaking selectors by a known registering device which is connected with the first group selector through a service selector, and is illustrated in Fig. 3 within the area enclosed by the dotted line. This known registering device is used according to the invention in such a manner that the registering device is not released after giving out the impulse train, but in the case of setting up an unsuccessful call repeats the impulse transmission at definite intervals of time.

Subscribers stations entitled to waiting service are connected to special first group selectors IGW'l', while the other subscribers stations are connected over the usual group selectors as for example is illustrated in loc. cit. The registering relay set can be used in common by privileged and non-privileged subscribers.

The switching proceedings are as follows:

When the subscriber N'i entitled to waiting service removes his receiver he is connected to a first group selector IGWl in the known way over a preselector VW'i. Relay TN is thus energized. After switching through relay A'l energizes over the circuit: pole, winding I of relay Al, contact 'iflpw, brush a of the preselector VWl, winding I of meter Z, subscribers station N'l, brush 1) of the VW'l', contact I lpw, winding II of relay Al, pole. Winding II of meter Z is connected over contact mm in an opposing circuit. At contact 520.1 the slow acting relay VA is switched on over a resistance, so that the service selector DW is started up: pole, driving magnet DDW of the service selector, automatic interrupter contact iiidw of the service selector, contacts 1422a, lipdw, brush liiclw, -1- pole, forming the engaged potential of a service selector. If the brushes of the service selector are standing on a free registering device, the driving magnet of the service selector receives no current. In this case, however, testing relay PDW energizes in the circuit: pole, contacts 'llpw, 180a, relay PDW, contact 'lSdw, magnet DDW, pole. The magnet DDW does not energize in this circuit. Contact ISpdw connects locking potential to the brush 16dw so that service selectors working in parallel are switched on to another registering device as described above. Contact 86 to iiipdw connect the seized first group selector IGWT to the registering relay set. Relays So and CU are thus energized over the circuit: pole, relays SA and CU, contact 82211110, brush 83dw, contacts 841', 85ft, pole. Relays EU and HW do not, however, energize at first because the circuit connects pole to both sides of them. Relay HW is the only relay which has been attached to the normal recording devices in order to enable it to effect the periodic repetition of the impulse transmission. Apart from this, alteration of the wiring of a normal registering relay set, occurs only at contacts 85 to 89hr.

On dialling the individual magnets SP of the different registering selectors are set: pole, contacts Sta'l, iiiva, tiipdw, brush 92dw, brush 93scm of the incoming control switch, magnet SP, pole. The incoming control switch is advanced one step forward by each impulse train in the known way, in order to connect up a fresh registering selector to the impulse contact 90611, so that the impulse trains are taken up by the registering selectors one after the other. The

transmission of the registered impulse trains takes place under the control of an outgoing control switch Sat and an assessor, not shown in the figure. The impulses are generated at contact 8M of the registering device. The first outgoing impulse train sets the first group selector IGW. The circuit is as follows: pole, contacts 85 8, 842', brush fiiidw contact 82pdw, slow acting relay CU, relay SA, pole. Contact 94.8w, Fig. 4, operates the slow acting relay VB during the impulse train, over the circuit: pole, contacts 95s, i53sa, slow acting relay VB, pole. On each impulse the vertical magnet of a group selector, which is constructed as a Strowger selector, is energized pole, vertical magnet I-I'l, slow acting relay U1, contacts 9611b, SIpdw, 9480;, 95s, pole. At the same time the slow acting relay U! is energized in this circuit. Relay CU holds up during the impulse train.

After the first impulse train relay U1 releases. During the impulse train relay E. was energized over: pole, relay El, oif normal contact 98k which was closed onthe first vertical step, contacts Hiflu'l, lilil ta, pole. After the release of relay U the rotary magnet D1 of the group selector receives current over the circuit: pole, magnet D1, contacts 102e, 9914], 10mm, pole. The testing brushes of the group selector IGW'I moves to the 1st contact, which may be engaged. At the same time contact Iilld'l of the rotary magnet Dl is still open so that relay E deenergizes. The circuit for magnet D1 is thus broken at contact lilZe'i. The rotary magnet releases, contact Ilildl again closes, and relay E receives current over the circuit: pole, relay E1, off normal contact 98k, contacts lllld'l, I038, brush 0, pole with engaged potential. Relay E closes the circuit for magnet D'i afresh. If the second line, on to which the rotary magnet now advances the brush, is free then relay S energizes, the circuit being: pole, contact lllflva, relay S, contacts |ll|d1,'98lc, relay E, pole. Relay S has so high a resistance that relay E cannot energize again in this circuit. At contacts I84 and l05s the drop to the following group selector or to the final selector LW'I is switched through. The connecting lines to the subsequent selectors are assumed in the embodiment to consist of two leads. At contact I868 the guarding potential is connected to the multiple field of the C-lead; brush of the group selector GWI, contacts l 868, 18nd, pole. Contact 858 opens the circuit for the slow acting relay VB, so that this deenergizes. In the bridge across the outgoing double lead connecting line lies winding I of relay F1. This, however, does not operate for the present in the loop circuit because winding I opposes winding II, for which the circuit runs: pole, winding II of relay F1, contact l95s, pole.

The'subsequent outgoing impulse'trains from the registering device are transmitted at contact lfllsa to the subsequent selectors, in the case of the embodiment to final selector LW'l. In the final selector whose switching means are illus trated in detail in Fig. 144 100. cit., the first impulse train is imparted to the vertical magnet H8 in the known way. The impulses. take the following course: -'pole, winding I of relay A8, contact ill8yt, brush a. of the first group selector IGWl, contacts I848, [818a, winding I of relay F1, contact I853, brush b of the first group selector, contact M9118, winding II of relay A8, pole. The slow acting relay V8 has already been operatedat contact M8 on the seizing of the selector. The first impulse to the vertical magnet takes the following path: pole, contacts ltaB, H5128, ofl normal contact 2%, winding II of relay U8, vertical magnet H8, pole. Relay V8 energizes'in this circuit so that the subsequent impulses are transmitted over the following circuit after the switching over of 01f normal contact 2k: pole, contacts IlOaB, I118, 3k, H4u8, winding II of relay U8, vertical-magnet H8, pole. The units impulse train is transmitted tothe rotary magnet D8 in the known manner. 'The switching of the impulse contact is effected at contact Il5u8: pole, contacts H0118, E08, lltk, H5u8, llfigil, Hist, rotary magnetDB, pole. The slow acting relay E8 is energized-in parallel with the rotary magnet.

In the first place it will be assumed that the selected line of subscriber N8 is free. The engaged relay G8 whose switching is described below, does not energize-in this case. Relay S energizes in known manner, since the circuit is not broken at contact I [8518. The line is switched through at contacts H888 and l29s8. Subscriber N8 is rung in the known way.

In the registering relay set the release relay L is energized in the known way, which will not be explained further here. The circuit for relay L is at once completed at contact 81hw', since relay HW is in the rest condition.

011 the reply of the desired subscriber N8 relay Y8 energizes and at contacts I2! and |22y8 the feeding current of the final selector is reversed for the duration of the conversation. Relay Fl of the first group selector accordingly energizes over winding I which now acts in the same direction as winding II. Relay FF and the thermo relay WH are operated over contact l 23]1: pole, thermo relay WH, relay FF, contacts l23f'l, l39bu,- liwva, pole. The thermo relay operates after about one second and energizes relay PW (Fig. 4) at contact I24wh: pole, relay PW, contacts l25pw, pole. Relay PW locks up over its contact l26pw, in the circuit: pole,relay PW, contacts l26pw, I06s, lflflva, pole. Relay PW reverses the feeding bridge of the calling subscriber N! at contacts I21 and lZBpw, so that the meter energizes in the known way, since the winding I is now energized in the same direction as winding II, operated over contact l29tn. Furthermore the circuit for relay PDW is broken at contact llpw so that this relay deenergizes, the seized registering relay set is released, and the latter is ready for another call.

If, however, the desired connection with subscriber N8 is engaged relay G8 energizes in the selector. It energizes while the final selector stands on the desired contact and before i the slow acting relay E8, energized during the units impulse train, has deenergized. The circuit is: pole, relay G8, contacts |30s8, l3le8, c-brush of the final selector, pole, being the engaged potential. After the release of relay E8, and thus after the termination of the units impulses train relay G8 still holds up over: pole, relay G8, contact 130.98, l32g8, I33v8, pole. The following circuit is completed for relay Y8: pole, winding I of relay Y8, contacts l3 lu8l, I35e8, 13698, pole. Relay Y8 reverses the feeding bridge at contacts I 2| and l22y8 as described in the case of the metering. The following circuit for winding I of relay U8 is completed over contact [3108: pole, relay U8, contacts l38e8, I3'lg8, relay E8, and parallel to the last over contact H188, rotary magnet D8, to pole. Relay U8 energizes in this circuit but only partially since it is constructed as a two stage relay. At contact IMuGI, which alone changes its position at the first stage, it breaks the above circuit for winding I of relay Y8. Relay Y8 accordingly again releases after a fraction of a second. The feeding bridge is thus again reversed. The reversal of the feeding bridge which as described above serves for metering is thus only established for a short time in the present case and serves for the initiation of the waiting condition. In the first group selector IGWl relay F'l energizes over winding I during the short reversal condition and at contact l23f1, closes the circuit for relays FF and WH. Relay WH however, does not energize this time, because contact I231? immediately returns again to the rest position and completes the following circuit for relay AU: pole, contacts 4000a, l39bu, l23fl', Mllsa, llff, relay AU, pole. Relay AU closes the following circuit: pole, resistance, contact I42au, I43bu, relay BU, contacts lddcu, 8lpdw, brush MEdw, relay HW, pole. Relays BU and HW energize, so that by the energized condition of relay HW in the registering relay set the waiting condition is characterized, contact I 46bu closes a locking circuit for relays BU and I-IW over the thermo relay THI. Relay F1 again deenergizes and breaks the energizing circuit of relay AU at contact Mlff.

On subscriber N8 testing engaged, subscriber N'l receives the engaged signal over contact Ml'gll and replaces the receiver. Relay A1 accordingly releases as does relay VA whose circuit is broken at contact 12:11. At contact Mona the circuit for relay S is broken. The latter deenergizes and at contacts 184 and I058 interrupts the circuit to the subsequent selectors, so that these release. The first group selector IGWT also releases since the release magnet is operated: pole, contacts l ifimw, ltllva, off normal contact l58lc, release magnet M, pole.

During the waiting condition the preselector remains set up and TN remains energized over contact l5lbu. In the first group selector IGW relays SA and CU are energized: pole, relays SA and CU, contacts 82pdw, 83dw, 85ft, pole. Later relays BU and AW in the above mentioned circuit and relay PDW in the circuit pole contacts l52bu, relay PDW, contact ltdw', magnet DDW, pole, are all energized. Finally relay VB locks up in the following circuit: pole, contacts 95s, l53sa, relay VB, pole.

If in this condition the calling subscriber takes up the receiver in order to set up a new call, he is connected up to a new registering device. On removing the receiver relay A'i energizes. Relay PDW is short circuited over contacts I5 lk, l55a'l, lfifibu. Contact filpdw'breaks the circuit for relays EU and I-IW. In the registering device contact 8lhw for the release relay L closes, so that the latter can energize in the known manner and release the registering device.

Contact Q'ipdw opens the energizing circuit for the vertical magnet I-I'i, before the closing contact 948a can effect the energizing of the vertical magnet. Contact 155a? connects the magnet DDW of the service selector to the automatic interrupter circuit: pole, contacts 56K, l55al, IBGZm, lsdw magnet DDW, pole. The service selector is set on a new free registering device, whereby the calling subscriber need not wait for the release of the switches of the registering device previously seized.

Normally, however, the calling party waits for the dialled subscriber N8 to become free. The latter is rung again at intervals of, for example, one minute. The time is governed by a time switching device Min which normally serves to release the registering relay set in the known way in case the calling party does not dial after seizing the registering device. The same time switching device is also used according to the invention for repeating the setting up of the call at definite intervals of time. If one minute is the interval chosen, then contact Min must be closed every minute.

After all the impulse trains have been transmitted to the speaking switch the outgoing control switch Sab stands on the last contacts. After the initiation of the waiting condition which is characterized by the energizing of relay HW, the following circuit is completed on the closing of contact Min: pole, contact Min, contacts [5767, Will, I5Sg5, winding II of relay G5, pole. Relay G5 is constructed as'a two stage relay and energizes partially. It only closes contact lfiflgtil. Winding I of relay G5 is thus connected on both sides to pole: on one side over contacts [5895, 5581?, lfilell, Min and on the other side over contacts W395i, Nile, 867m last contact of brush I 628a?) of the outgoing control switch, segment of brush flotsam of the incoming control switch, contact i641. When contact Min again opens, winding I of relay G5 also receives current pole, winding I and II of relay G5, to pole over the path just described. Relay G5 energizes completely and closes contact I 65g5, when contact Min again closes after one minute the following circuit is completed: pole, contacts Min, ltle'l, i58l, iii5g5, ldtfil, off normal contact liillc of the registering selector which is first set up, BQhw, brush liiiisab, automatic interrupter contact SU, magnet Sub of the outgoing tool switch, pole. The control switch makes one step so that it reaches its starting position. Brush |62sab thereupon opens the circuit for relay G5, which releases and is ready erful buzzer tone in his for the next period. The outgoing control switch now proceeds through its v switching positions again one after the other as on the first setting up of the call, whereby the impulse trains are transmitted by means of, an assessor in the known manner. Contact S li serves as. the impulse contact, the known control of which will not be further described.

In the first group selector IGW relay MW is energized on the first impulse of the first repeated setting up of the call in the following way: the first impulse energizes. relay U? in the circuit of the vertical magnet H! as described above. After the vertical motion contact 9870 is closed so that the following circuit is completed: pole, relay El, contacts 98k, ltlilul, 675m, lfiibu, ill/ c (this off normal contact operates after ofi normal contact 98k) ll2sb, winding I of relay MW, con tacts i'lfibu, I'Jibu, pole. Relay MW energizes in this circuit and locks up over its winding II and its contact I'Mmw: pole, winding II of relay MW, contacts I'Mmw, [128b, winding I of relay MW, contacts l'iiibu, ifiibu, pole. Contact MBmw breaks the release circuit for magnet M before off normal contact Mills can close.

On the first setting up of the call pole was connected to contact 1012a for setting the rotary magnet D1; Instead of this pole is now connected over contacts llEva, Hilbw, I 16k, I'Hmw. The other proceedings take place just as in the first establishment of the call.

If the subscriber N 8 is again engaged the brief reversal of polarity of the feeding bridge is again elfected. The result of this is, as has been described, not the metering but the energizing of relay AU. Relay SB is energized over contact Kilian and at contact l 1281) breaks the locking circuit of relay MW. On its release relay MW completes the release circuit of the first group selector IGW: pole, contacts l itlmw, Mlloa, ifiilk, release magnet M, pole. Contact ll'lmw breaks the locking circuit for relay S. Thereupon the same condition is established as after the first unsuccessful call. The time switch Min of the registering device then again initiates another setting up of the connection after one minute.

In the event of the call being successful, and the desired connecting line of subscriber N8 is found to be free, relay G8 does not energize, but instead relay S8 of the final selector. The brief reversal impulse is thus not transmitted in this case. Relay Y8 only energizes on subscriber N8 replying and then finally reverses the feeding current. Relay Fl is energized for a prolonged period. The thermo-contact relay WH moves to its end position. Relay PW locks up over the circuit: pole, relay PW, contacts E and 1261020, H368, l'it'ma, Elfibu, l'ltlc, l'llmw, pole. Contact llilpw short circuits relay CU through contact H9003. Relay CU de-energizes. Contact i liicu opens, but relays BU and HW remain held over contact iwoa. At contact ifiicu a buzzer circuit is completed for winding III of relay Al: buzzer contacts I'iZbu, lfllcu, winding III of relay A'i, plus pole. The buzzer signal is transmitted from winding III to windings I and II of relay Ali. Subscriber N'i thus receives a powteleph'one. The latter stays connected to the line through a condenser which tunes the circuit to the buzzer frequency. The subscriber takes up his receiver. Relay Al thus energizes and at contact 72a! completes the energizing circuit for VA. The latter breaks the locking circuit of relays BU and HW at contact til .scriber receives ring back in [802211. On releasing the registering 'device releases relay HW. .The release circuit for the group selector is broken at contact 90a. The connection is held through contactrtilflva. Relay BU'which releases at the same time as relay HW, opens the locking circuit for relay MW at contact I'l3bu. On the opening of contact I52bu relay PDW releases since contact limo-has al ready opened, on the desired subscriber replying, an account of the energizing of relay PW.

An automatic release of the connection after a giventime by means of a hot wire contact TH'I, for example, after 10 minutes, is provided to meet the case in which the calling subscriber does not reply to the ring-back, or the called subscriber is not obtainable. As mentioned above, relay BU is energized during the waiting condition. Through contact l lfibu the following circuit is established; for TI-l'l: pole, hot wire relay THl, contact Mfibu, relay BU, contacts l80va, Blpdw, brush M5dw, relayHW, pole. After the definite time which can be determined as desired, the hot wire contact operates and operates contact l8lth1. Relay BU is short circuited. At contact l13bu the locking circuit for relay MW is broken. The release circuit is completed at contact MBmw. Contact l52bu opens the circuit for relay PDW, so that the registering device also releases.

In the embodiment described the connection is always released if the desired subscriber is found to be engaged. The device can also be made so that the release is effected if the subscriber does not reply within a given time. Such an arrangement has the advantage that an absent subscriber is rung at definite intervals until he returns to his'apparatus and replies. Limits are thus practically removed to the time during which the registering device is seized or the duration is made of considerable length, so that the calling subscriber can Wait for hours for the reply of the desired subscriber. Also withthis arrangement the telephonesystem is not seriously encumbered because the connecting path is always only set up transitorily. The larger the time interval between the individual establishing of the connection, the smaller are the claims on the system.

A system suitable for registering forms'the basis of the embodiment. Clearly the invention can be applied to other systems. In this case only the subscribers entitled to waiting service have access to the registering devices, while the other subscribers set up, their calls directly. The registering devices can be attached individually to the subscribers stations or in common to several of the latter.

It was further assumed in the embodiment that the seized registering device became free when the calling subscriber started a new call during the waiting period. The arrangement can also be made for the registering device to remain seized in this case so that the subscriber can complete another call in the waiting period and therefore still remain ready to receive the ring back. When the connection periodically set up by the registering device is successful, the calling subthe way described through the buzzer current, which is also received if he has just held another call. He can then establish the connection with the originally desired subscriber by replacing the receiver and then removing it again.

Privileged subscribers can, if they so wish, be provided with more than one registering. device so that the subscriber can call several stations one after the other and wait for the ring back from these. I l

.In the embodiment accord'mg to Figs. 3 and 4, the numerical registering device is merely connected to the calling subscriber through preselecting devices. The arrangement can also be made so that the station entitled to call registering has to select the numerical registering device by. meansof impulses. Then the connection between the waiting station and the numerical registering device need not remain. seized during the waiting period, if the registering device is provided with additional registering means in this case, which take up the number. of the waiting station for example on the waiting subscriber dialling his own number after that of the desired subscriber. After the connection with thezdesired subscriber has been set up by the numerical registering device, the latter finally effects the selecting for the waiting subscriber so that both subscribers are connected together, for exampleovera repeater.

Theadditional registering device for the call number ofthe waiting subscriber can also be employed". when the registering device is connected to the privileged station automatically. In this casethe'autcmatic connecting device can be released after the registering has taken place.

Having described the invention, what is con sidered to'be new and is desired to be protected by Letters Patent, will be set forthin the following claims:

What isv claimed is:

1. In a telephonesystem, a calling and a called line, automatic switching mechanism controlled by said calling line for interconnecting said lines,

means for automatically registering a call from said calling line to said called line in case-the called line is busy, said means responsive to the replacement of the receiver at :the calling line telephone, and means for signalling the'calling line when the called line is no longer busy.

2. In a telephone system, a calling and a called line, automatic switching mechanism controlled by saidpcalling line for interconnecting. said lines, means for automatically registering a call from saidcalling line to said called line in case the called line is busy, said means responsive to the replacement of the receiver atthe. calling line telephone, means for signalling the called line when it is no longer busy, andmeans responsive to the answering of the called line'for signalling the calling line.

3. Ina telephone system, a calling and a called line, automaticswitching mechanism controlled by the calling line for interconnecting said lines, means in said mechanism for testing said called line for its busy or idle condition, means for registering a call in case said called line is busy, means for signalling the called line when it is no--longer busy, and means controlled by said testing means for signalling said calling line while the receiver thereof is on the switchhook when the called line responds.

l. 'In a telephone system, a calling telephone and a called telephone, automatic switching mechanism controlled by the calling telephone for interconnecting said telephones, means for automatically registering a call from the calling telephone to the called telephone in case the called telephone is busy when it is called, means for signalling the called-telephone whenit is no longer busy, means for signalling the calling telephone when the called telephone responds, and

means for enabling the calling telephone to engage in connection with the other telephones during the time the called telephone is busy.

5. In a telephone system, a calling and a called telephone, automatic switching mechanism controlled by the calling telephone for interconnecting said telephones, means for automatically registering a call between said telephones in case said called telephone is busy, means for signalling the calling and called telephones when the called telephone is no longer busy, and means for permitting the calling telephone to engage in connections with the other telephones during the time the first called telephone is busy.

6. In a telephone system, a calling and a called telephone, automatic switching mechanism controlled by the calling telephone for interconnecting said telephones, means for automatically registering the call when the called line is in a busy condition, and a timing device started into operation at the time of the registering of the call for releasing the automatic switching mechanism in case the called telephone does not respond'within a definite time interval.

'7. In a telephone system, a calling telephone and a group of called telephones, automatic switching mechanism controlled by the calling telephone for connecting with any idle one of said group of called telephones, means for automatically registering the call in case all of the telephones of the group are in a busy condition, means for maintaining the connection established with the last busy telephone of the group, and means for transmitting signalling current to the called and calling telephones when the busy telephone becomes idle and while the receiver of the calling telephone is still on the hook.

8. In a telephone system, a calling and a group of called telephones, said group of called telephones including a main station, automatic switching mechanism controlled by said calling telephone for connecting with the main called station, means controlled by the main station for extending the call to any idle one of said called telephones, automatic means for registering the call in case all of said group of called telephones are in a busy condition, said calling telephone and main station thereupon replacing their receivers, means when one of the called telephones becomes idle for signalling the same, and means operated when said called telephone answers for signalling the calling telephone.

9. In a telephone system, a calling and a called telephone, automatic switching mechanism controlled by the calling telephone for establishing a connection with the called telephone, means for registeringthe call in case the called telephone is in a busy condition, said calling station replacing its receiver, means for signalling the called station when it is no longer busy, and means operative when the called station answers for signalling the calling station, the signal of the calling station being effective through operation of its receiver.

10. In a telephone system, as claimed in claim 9 in which the receiver of the calling station is included in a circuit tuned to the frequency of the calling signalling current.

11. In a telephone system, calling telephones divided into two groups, called telephones, automatic switching mechanism controlled by a calling telephone of any of the two groups for establishing a connection with a called telephone, means for registering the call in case the called telephone is busy, said call registering efiective only when a telephone from a particular one of the groups is calling, means for signalling the called telephone when it becomes idle, and means operated when the called telephone answers for signalling the calling telephone.

12. In a telephone system, a called and a calling telephone, automatic switching mechanism for interconnecting said telephones, means for registering the call in case the called telephone is busy when called, automatic means controlled by said registering means for periodically setting up the connection to the called line as long as it is busy, means operated when the called telephone becomes idle for signallingthe same, and means operated responsive to the removal of the receiver of the called telephone for automatically signalling the calling telephone.

13. In a telephone system, a calling and a called telephone, automatic switching mechanism controlled by the called telephone for establishing a connection with said called telephone, automatic storing mechanism for automatically registering the call in case the called telephone is busy, means in said storing mechanism for periodically setting up a connection with the called telephone to see if it is idle, means controlled by said storing mechanism to signal the called telephone when it becomes idle, and means controlled by the storing mechanism to thereupon set up a connection with the calling telephone and to signal the same.

FRITZ LUBBERGER. BENNO J OI-IANNESSON. 

